Permanently lubricated film gasket and method of manufacture

ABSTRACT

A permanently lubricated film gasket for providing a fluid-tight seal between a corrugated pipe and a smooth annular section of an outer pipe or section when the corrugated pipe and the outer pipe or section are in a relative surrounded and surrounding relationship. A first portion of the gasket is shaped to fit within a groove or recess of the corrugated pipe. A second portion of the gasket extends from the first portion. The second portion is at least partially comprised of permanently lubricated film for facilitating in the connection of the pipes along a single direction.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application is a continuation-in-part application containingcommon subject matter as previously filed and co-pending applicationSer. No. 10/419,541, filed in the U.S. Patent and Trademark Office onApr. 21, 2003, entitled “PERMANENTLY LUBRICATED GASKET”, which is acontinuation-in-part of U.S. application Ser. No. 09/998,697, filed inthe U.S. Patent and Trademark Office on Nov. 30, 2001, to issue as U.S.Pat. No. 6,550,775, entitled “ANNULAR GASKET,” which is acontinuation-in-part of U.S. patent application Ser. No. 09/726,814filed in the U.S. Patent and Trademark Office on Nov. 30, 2000, entitled“ANNULAR GASKET WITH LOCKING STRUCTURE,” now U.S. Pat. No. 6,367,802.The present application claims priority the aforementioned patents andpatent applications, which are incorporated in their entirety herein byreference for all purposes.

TECHNICAL FIELD

The present invention relates to elastomeric gaskets for providing aseal between a pair of tubular members and, more specifically, to agasket having at least a portion being made from thermoplastic embeddedwith a lubricating chemical film that permanently imparts properties ofa lubricant from the gasket to the contacting surface of one of thetubular members.

BACKGROUND ART

It is well known to form a seal between two pipe sections, such as twocorrugated pipe sections, where the end of one of the pipe sections hasannular grooves and one of the pipe sections has an enlarged bellportion at one end. Some prior art elastomeric gaskets are placed aroundthe end of the pipe section having annular grooves. The pipe sectionhaving annular grooves is inserted into an enlarged bell portion of asecond pipe section. The elastomeric gasket contacts each of the pipesections to form a seal between the pipe sections.

Typically, a large frictional force is encountered when the inner pipeand the elastomeric gasket is inserted into the outer pipe. As one endof the inner pipe is pushed into the enlarged end or bell of the outerpipe section or pipe connector, the gasket is sometimes pulled from thegroove by the large frictional force. When the pipe is not properlysealed, ground water may leak into the pipe or fluid may leak out of thepipe and contaminate the ground.

Lubricant has been manually applied to elastomeric gaskets before theinner pipe and the gasket is inserted into the outer pipe. The lubricantreduces the frictional force between the gasket and the outer pipe. Thereduced frictional force reduces the likelihood that the gasket will bepulled from the groove by the frictional force. The manual applicationof the lubricant is labor intensive and is usually performed in a trenchor ditch making the lubricant susceptible to being removed by waterfrequently found in such environments. In addition, the manually appliedlubricant is wiped from the gasket if the pipe joint is disassembled. Asa result, the lubricant must be reapplied before the pipe joint isreassembled.

Costly secondary operations have also been developed for applyinganti-frictional coatings to gasket surfaces. A secondary operationoccurs when the lubricant is applied to the gasket after the gasket iscured. An example applying a lubricant in a secondary operation appearsin U.S. Pat. No. 6,328,309 to Corbett. In particular, Corbett depicts aspray-on lubricant that is applied after the gasket is hardened.Secondary operations as taught in Corbett typically require additionalsteps such as heat treatment and/or prescribed cooling periods beforethe product is finished. In addition, the spray operations lack theability to control the thickness of the lubricant coatings and thecoatings often crack inhibiting the gaskets ability to stretch orcompress without resulting in seal failure.

Prior art methods have been developed that self lubricate gaskets asthey are assembled. For example, U.S. Pat. No. 4,365,818 to Tolliverdiscloses a seal including a cavity containing a lubricant, which isreleased when one pipe joint is slid over the seal. U.S. Pat. No.5,143,381 to Temple is directed to a seal, which has an internal chambercontaining a lubricant. A slit in the body of the seal extends into thechamber. When one pipe is moved over another pipe end, the slit isspread, thereby releasing the lubricant against the sealing surface.U.S. Pat. No. 5,626,349 to Sutherland et al. concerns a sealing ringcontaining a lubricant enclosed within a membrane formed on the ring'sbody. When a connecting pipe is slid into the pipe joint, the membraneis ruptured, releasing the lubricant and reducing the frictional forcesimparted on the sealing ring during the joining of the pipes. U.S. Pat.No. 5,735,528 to Olsson discloses a seal containing a lubricant. Thelubricant migrates to the surface of the seal, thereby providingself-lubricating properties. Each of these methods provide the lubricantonly the first time, or a limited number of times, the gasket forms aseal. The lubricant is eventually wiped off or spent. After thelubricant is wiped off or spent, a lubricant may need to be manuallyapplied to ensure a proper seal.

In Applicant's co-pending application Ser. No. 10/419,541, filed in theU.S. Patent and Trademark Office on Apr. 21, 2003, entitled “PERMANENTLYLUBRICATED GASKET” incorporated herein by reference uses a lubricatingagent additive that migrates to the surface of the gasket. This approachlowers the coefficient of friction “COF” and allows the pipe to beassembled without lubrication. The migration results in an oily textureon the surface of the gasket that can be undesirable in certainapplications.

Another potential shortcoming of using a migrating lubricating agent oradditive is creating a condition having a heightened disposition tocontamination. A migrating lubricant agent produces an oily texture onthe gasket surface that attracts dust and debris, which can lead toleaks and failure in the pipe joint when assembled. There also exists aproblem of chemical migration to areas undesirable of lubrication.

There is a need for a gasket combined with a permanent lubricatingchemical film resistant to contamination and propitious to weldingoperations while maintaining lubrication regardless of the frequencythat the joint is assembled and disassembled. In addition there exists aneed for a gasket to include a lubricating portion that is integratedwithin the gasket during the extrusion process eliminating a need forlabor and cost intensive secondary operations. While yet a need existsfor a gasket having a lubricated portion susceptible to compression andexpansion without cracking, while retaining lubrication within acontrolled location.

SUMMARY OF THE INVENTION

The lubricated film gasket concerns a permanently lubricated annulargasket for providing a fluid-tight seal between an inner pipe and asmooth annular section of an outer pipe or section when the corrugatedpipe and the outer pipe or section are in a relative surrounded andsurrounding relationship. A first portion of the gasket is shaped to fitwithin a groove or recess of the corrugated pipe. A second portion ofthe gasket extends from the first portion. The second portion includes aleading edge partially comprised of a permanently lubricating chemicalfilm. The second portion is configured to make sealing contact with theouter pipe or section when the corrugated pipe and the outer pipe orsection is in a relative surrounded and surrounding relationship.

In one embodiment, the first portion, second portion, and permanentlylubricating chemical film are combined during the injection moldingprocess. In this embodiment, the first portion has a first durometer andthe second portion has a second durometer that is less than the firstdurometer. In this embodiment, the second portion may include anon-lubricated portion and a permanently lubricated portion that ispermanently lubricated by the lubricating chemical film. In thisembodiment, the gasket may be tri-extruded such that the permanentlylubricated chemical film is embedded within a substantial portion of theleading edge of the second portion and the lubricating film, secondportion, and first portion are formed together during a single extrusionoperation.

In another embodiment, the permanently lubricated annular gasketincludes a single body portion of a particular durometer suitable suchthat the body portion is capable of residing within a recess of an innerpipe at a first end and creates a sealing engagement with at coactingouter pipe at a second end. The permanently lubricated chemical film iscoextruded with the body portion along a substantial portion of aleading edge at the second end during a single extrusion operation.

In an alternative embodiment, the permanently lubricated chemical filmis coextruded with the second portion. Subsequent to the forming of thechemical film within the second portion is the coextruding of the secondand first portions.

In another embodiment, the second portion and the permanentlylubricating chemical film are joined at a die head or through aninjection mold process. Such approach eliminates the need for any laborand cost intense secondary operation.

In yet another embodiment the lubricating film is made from materialshaving a low COF and more specifically a value of 0.5 or less. In oneembodiment the COF is preferably 0.3. Examples of suitable low COFmaterials include polypropylene or polyethylene, which typically providea 0.3 COF value. The lubricating film is combined to the second portionalong a substantial portion of the leading edge and the film comprises avery thin layer ranging from 0.001″-0.010″ and preferably having athickness between 0.003″-0.005″.

Another feature is that in most applications the lubricating film formsa protective shell over the gasket minimizing the potential for tearingor cuts in the material. Yet another feature of the lubricating film isthe ability to integrate the film to controlled areas along the leadingedge of the second portion, thereby allowing a trailing portion of thesecond portion to lock or grip the pipe when forces are applied oppositethe direction of the lubricating film.

Another feature is the controlled placement and static characteristicsof the lubricating film, which substantially reduces the potential forfailure when performing welding and joining operations to the ends ofthe gasket.

These and other advantages and features of the exemplary embodiments ofthe lubricated film gasket and method of manufacture are described indetail in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a portion of the annular gasket of oneembodiment of the present invention;

FIG. 2 is a cross section of the elastomeric gasket of one embodiment ofthe present invention;

FIG. 3 is a sectional view of a gasket of the present inventioninstalled on a corrugated pipe;

FIG. 4 is a sectional view of a gasket of the present inventioninstalled on a corrugated pipe, and engaged by an enlarged end of asecond pipe;

FIG. 5 is an enlarged fragmented view of FIG. 3;

FIG. 6 is an enlarged fragmented view of FIG. 4;

FIG. 7 is a side view of the elastomeric gasket of another embodiment ofthe present invention; and

FIG. 8 is an enlarge view of the elastomeric gasket and coacting tubularmembers reacting to separation forces.

DETAILED DESCRIPTION OF THE PREFERRED EMOBODIMENTS

The present invention is directed to a permanently lubricated filmannular gasket 10, depicted in FIGS. 1 and 2, for providing a fluidtight seal between a first tubular member 12 and second tubular member18, as shown in FIGS. 3 and 4. In the illustrated embodiment, the firsttubular member has a plurality of annular grooves 14 and ridges 16 andthe second tubular member includes a smooth annular section 20, such asa bell.

Referring again to FIGS. 1 and 2, the annular gasket 10 includes afirst, support portion 24 and a second, elastomeric gasket portion 26.The support portion 24 is made from a material having a first,relatively hard, durometer. The elastomeric gasket portion 26 is madefrom a relatively soft, durometer material, and includes a leading edge13 a and oppositely positioned trailing edge 13 b. Formed along asubstantial portion of the leading edge 13 a of gasket portion 26 is apermanently lubricated film 11. The permanently lubricated film could bemade from any material having a low coefficient of friction “COF”, andmore specifically level of 0.5 or less. In one embodiment the COF ispreferably valued at approximately 0.3, which would include materialssuch as polyethylene or polypropylene. The permanently lubricated filmis relatively thin, having a thickness range between 0.001″ to 0.010″preferably ranging between 0.003″ to 0.005″ thick, and is typicallyapplied along a substantial portion of the leading edge 13 a.

The lubricating film 11 reduces the COF between tubular members 12 and18 during the interconnecting of the members. Because the lubrication isproduced from a film, the target areas for lubrication can be controlledand isolated. This provides several advantages such as a reduced risk offailure at welded connections because the joining portions of thegaskets are virtually lubricant free, unlike self-lubricating gasketswhere the lubrication tends to migrate into undesirable areas. Anotheradvantage of film lubrication is that after the pipe is assembled, thenon-lubricated trailing edge 13 b acts as a lock, gripping the pipe,thereby resisting separation between the tubular members. Yet anotheradvantage of the film lubrication is the ability to simultaneouslyextrude the lubricating film with any number of desired extrudates, thuseliminating costly secondary operations for applying lubrication to agasket.

The figures illustrate one example of a physical configuration of apermanently lubricated gasket. However, the inventive permanentlylubricated film gasket 10 could take any physical form without departingfrom the spirit and scope of the claimed invention. Referring to FIGS. 4and 6, the illustrated permanently lubricated film gasket 10 seals a gap21 between the first tubular member 12 and the smooth annular section 20of the second member 18 when the first tubular member and the smoothsection are in a relative surrounded and surrounding relationship. Inthe illustrated embodiment, the second tubular member 18 is a corrugatedpipe having an integral bell or large end that is not corrugated. In analternate embodiment, the integral bell or large end includescorrugations that strengthen the integral bell or large end. In theillustrated embodiment, the first tubular member 12 is a corrugated pipethat includes a recess 22 in one of the ridges 16. It should be readilyapparent that the inventive permanently lubricated film gasket 10 couldbe used on any type of pipe. For example, the permanently lubricatedgasket could be used with PVC pipe, corrugated metal pipe, corrugatedplastic pipe, fiberglass pipe, or cast iron pipe. Further, it should bereadily apparent that the outer pipe could include corrugation(s) whilethe end of the inner pipe is smooth. For example, the permanentlylubricated gasket could be used to form a PVC bell and spigot joint.

In the illustrated embodiment, the support portion 24 includes an anchorportion 28 shaped to fit within the recess 22 in a ridge 16 of thecorrugated pipe and a tip portion 30 that extends radially outward fromthe anchor portion 28. In an alternate embodiment, (not illustrated) theanchor portion 28 is shaped to fit within a groove 14 in the corrugatedpipe. Referring to FIG. 5, the tip portion 30 is radially outward of theridge 16 when the anchor portion 28 is disposed in the recess 22 in theridge 16 or a groove 14 in the corrugated pipe.

The anchor portion 28 is shaped to fit within the recess 22 in a ridge16 in the corrugated pipe. The shape of the anchor portion 28 can bechanged to fit within recesses having different shapes or to fit withina groove 14 in the corrugated pipe. Referring to FIGS. 1 and 2, theillustrated support portion 28 includes first and second side surfaces32 a, 32 b, first and second intermediate surfaces 34 a, 34 b, and aninner surface 36. Referring to FIG. 5, the first and second sidesurfaces 32 a, 32 b correspond to first and second sidewalls 38 a, 38 bof the recess 22. The intermediate surfaces 34 a, 34 b correspond tointermediate walls 40 a, 40 b. The inner surfaces 36 correspond to abottom wall 42 of the recess 22. The anchor portion 28 includes an outersurface 50 formed by first and second radially outer lateral surfaces 52a, 52 b.

Referring to FIGS. 1 and 2, the anchor portion 28 includes an opening44. The opening 44 reduces the amount of material needed to form theanchor portion 28. In the illustrated embodiment, the opening 44 has atear drop shape. It should be readily apparent to those skilled in theart that any shape of opening could be used.

Referring to FIGS. 1 and 2, the illustrated tip portion 30 includes atransition portion 46 or neck portion and an end portion 48 that isrounded in the illustrated embodiment. The transition portion 46 is anarea of reduced thickness that extends from the outer surface 50 of theanchor portion 28 in the illustrated embodiment. It should be readilyapparent to those skilled in the art that the thickness of thetransition portion 46 can be varied to increase or decrease an amount offorce required to deflect the end portion 48. The end portion 48 extendsradially outward from the neck portion 46. It should also be readilyapparent to those skilled in the art that the end portion can be anyshape that holds a gasket portion in contact with the second tubularmember.

In the exemplary embodiment, a harder material typically having a rangeof 60-70 durometer is used to construct the support portion 24. Someexamples of a suitable material would include 70-durometer santoprene,styrene ethylbutylene styrene (“SEBS”), and thermoplastic vulcanizate(“TPV”). Use of a harder material for constructing the support portion24 increases the force required to fold the tip portion 30 over. Theresult is that a tighter seal is provided against the smooth annularsection 20 and the ridge 16. The material used in the support portion 24also reinforces the pipe corrugation, reducing the amount deflectionwhen pressure is applied. It should be readily apparent that otherfiller material could be used to construct the support portion 24 of thegasket 10. The elastomeric gasket portion 26 is made from a secondmaterial having a durometer that is less than the durometer of thesupport portion 24. In the exemplary embodiment the second elastomericgasket portion 26 is preferably made from a material having a 40 to 50durometer range. Some examples of suitable material include 40-50durometer santoprene, isoprene, and ethylene propylene diene monumer(EPDM). It should also be readily apparent that the support portion 24could be made from the same material that the gasket portion 26 toeliminate the coextrusion process between the support and gasketportions.

Referring to FIGS. 1 and 2, the gasket portion 26 is disposed on the tipportion 30 and the outer surface 50 of the support portion 24. Thegasket portion 26 is configured to make sealing contact with a ridge 16and the smooth annular section 20 when a corrugated pipe having a recess22 in which the gasket 10 is received and the smooth annular section 20of the second tubular member 18 are in a relative surroundingrelationship (see FIGS. 4 and 6).

The illustrated elastomeric gasket portion 26 includes first and secondleg portions 54 a, 54 b connected by a central portion 56. The centralportion 56 covers the tip portion 30 of the support portion 24. Thecentral portion 56 can be configured in any shape that makes contactwith the smooth annular section 20.

In the exemplary embodiment the permanently lubricating film 11 extendsfrom the radially outer surface 52 a to the central portion 56 of theleading edge 13 a of the gasket portion 26. It should be apparent thatit may be desirable to cover more or less of the surface area of theleading edge 13 a depending on the tubular member configuration andparticular application. The first and second leg portions 54 a, 54 bcover the radially outer surfaces 52 a, 52 b of the anchor portion 28and extend laterally of the first and second side surfaces 32 a, 32 b ofthe anchor portion 28. In the exemplary embodiment, the permanentlylubricating film 11, gasket portion 26, and the support portion 24 aretriextruded. In another embodiment, the support portion and the gasketportion are bonded together by some means other than co-extrusion. Thegasket may be attached to the support portion by adhesives or any otheracceptable attachment method.

The gasket 10 can be made by extruding a length of gasket material andconnecting its ends together by gluing, vulcanization, injectionmolding, or a welding process. For example, an annular gasket 10 for an18 inch pipe would be formed of a 57.5 inch of gasket material. Anannular gasket 10 for a 24 inch pipe would be formed from a 76.0 inchlength of gasket material. The annular gasket 10 can also be molded toeliminate the step of connecting the gasket ends, while remainingconducive to embedding the permanently lubricating film 11 along theleading edge 13 a of the gasket portion 26.

FIGS. 3, and 4 illustrate a coupling 58 formed with the disclosed gasket10. Although the gasket 10 could be used to form a joint between metal,concrete and other tubular sections, it is particularly well suited foruse with corrugated plastic pipe. The illustrated coupling 58 includes acorrugated pipe 12, an outer annular section 20 (a bell portion of asecond corrugated pipe in the illustrated embodiment) and an annulargasket 10. The corrugated pipe 12 has annular grooves 14 in ridges 16.In the illustrated embodiment, one of the ridges 16 includes a recess 22that receives an anchor portion 28 of the gasket 10. In an alternateembodiment, the anchor portion 28 is sized to fit within one of thegrooves 14 in the corrugated pipe. The annular section 20 is disposedaround the corrugated pipe 12. The annular gasket 10 is disposed betweenthe corrugated pipe 12 and the annular section 20. The anchor portion 28of the annular gasket 10 is disposed within the recess 22. The tipportion 30 of the support portion 24 extends radially outward of theridge 16. Referring to FIG. 6, the first and second leg portions 54 a,54 b are disposed on a ridge 16 and make sealing contact with a ridge16. The leading edge 13 a up through the central portion 56 of thegasket portion 26 form a sealing contact with the smooth annular section20. The lubricating film 11 facilitates in the sealing contact as thefilm lubricates the gasket portion 26 during the engagement process bymaking contact with inner surface 36 as best seen in FIG. 6.

Referring again to FIG. 6, the smooth annular section 20 or enlargedbell portion applies pressure to the central portion 56 of the gasketportion 10 and deforms the central portion 56. The tip portion 30 isharder than the gasket material, increasing the force required to foldover or bend the central portion 56 of the gasket 10. The increase inforce required to deform the central portion 56 results in a tighterseal between the central portion 56 and the bell of the second tubularmember and a tighter seal between the leg portions 54 a, 54 b and theridge 16.

In addition, since the material of the anchor portion 28 is harder thanthe gasket portion 26 material, the anchor portion 28 materialreinforces the pipe corrugation, reducing the amount of deflection ofthe pipe corrugation when pressure is applied. Referring to FIGS. 3, 4,5 and 6, the disclosed gasket 10 is used in a method of providing afluid tight seal between a corrugated pipe having a ridge 16 thatincludes a recess 22 and a smooth inner surface 36 of an annular section20 or bell portion. The support portion 24 of the gasket 10 is insertedinto the recess 22 of a corrugated pipe. The tip portion 30 of thesupport portion 24 extends radially outward of the ridge 16. The ridge16 is engaged with the leg portions 54 a, 54 b that are disposed on theradially outer surfaces 52 a, 52 b of the support portion 24. Thecorrugated pipe is inserted into a smooth annular section 20, such asthe depicted bell portion of a corrugated pipe having a smooth innersurface 60. The smooth annular section 20, or bell portion, engages thepermanently lubricated film 11 that extends along the leading edge 13 aof the elastomeric gasket portion 26. The central portion 56 of theelastomeric gasket portion 26 and the tip portion 30 of the supportportion 24 are deformed by the smooth annular section 20, or bell. Theharder tip portion 30 resists deformation and presses the centralportion 56 and gasket portion 26 tightly against the bell, therebycreating a tight seal between the central portion 56 in the bell. Theincrease in force required to deform the tip portion 30 presses legportions tightly against the ridge 16.

Referring to FIG. 5, is an embodiment where the first support portion 24is made from a material that is relatively hard durometer. For example,the support portion may be made from a material having a 70-durometerhardness. In this embodiment, the second gasket portion 26 is made fromthe elastomeric material containing the lubricating chemical film 11along a substantial portion of the leading edge 13 a of gasket 26 makingit permanently lubricated. However, the position of the permanentlylubricated chemical film 11 could be at any location on the gasketrequiring lubrication without departing from the spirit and scope of theclaimed invention.

Referring to the embodiment of FIG. 7, the permanently lubricated filmgasket 10 includes a single body portion 61 of a particular durometersuitable such that the body portion 61 is capable of residing within arecess 22 of a first tubular member 12 at a first end 62 a and create asealing engagement with at coacting second tubular member 18 at a secondend 62 b. The single body portion durometer can range at a levelacceptable to pipe standard specifications for elastomeric seals, ASTMF477 would include an example of such a standard. In the exemplaryembodiment, the preferred durometer of the single body portion wouldrange between 40 and 60 durometer on a Shore A scale. The permanentlylubricated chemical film 11 is coextruded with the body portion 61 alonga substantial portion of a leading edge 13 a at the second end 62 bduring a single extrusion operation. The permanently lubricated chemicalfilm 11 is formed only in portions of the second end 62 b requiringlubrication. The lubricating film 11 can be made from lubricatingmaterials having a reduced COF and in the exemplary embodiment ispreferably a level of 0.5 or less. Such materials include polypropyleneor polyethylene. The lubricating film is combined to the gasket 10 froma very thin film layer ranging from 0.001″-0.010″ and preferably0.003″-0.005″ thick. The geometrical features of the single body portionact in the same manner as the two-part extrusion gasket 26 and support24 portions already described in detail above. The single body portion61 eliminates the triextrusion process of the two-part extrusion andrequires only a coextrusion operation with the lubricating film 11 andsingle body portion 61.

FIG. 8 includes a triextruded permanently lubricated film gasket exposedto separation forces between the tubular members, as indicated by arrowsdepicting the relative forces imposed on the first tubular member 12 andsecond tubular member 18. Because the lubricating film is only locatedon the leading edge 13 a of the gasket portion, when the forces deflectthe central portion 56 and tip 30 in a direction away from thelubricated portion 11, the non-lubricated portion, particularly thetrailing edge 13 b acts as a brake. Thus, the absence of lubricationalong the trailing edge 13 b helps lock the tubular members together,thereby assisting in maintaining a sealing engagement.

The method of manufacture in the exemplary embodiment includes, at leastone polymeric material being loaded into a first extruder and apermanently lubricated film material being loaded into a second extruderhaving a common extrusion die head assembly with the first extruder. Inone embodiment the lubricated film 11 could be in a granular form priorto the extrusion process. The materials are located within therespective extruders and heated to a temperature range of 350 to 425degree Fahrenheit, resulting in a molten state for both the polymericand lubricating film gasket materials. Once the prescribed temperatureis reached, which in the exemplary embodiment is preferably slightlyabove or at 350 degrees, the polymeric and film gasket materials are fedthrough the common die head assembly, forming a single extrusion gasket10 with a lubricated film 11 embedded along a select portion of thegasket. After which, the extrusion is typically fed through a water bathfor cooling to a prescribed temperature level before being cut andwelded.

In another embodiment, the permanently lubricated film 11 is preformedprior to the extrusion process. As such, the film 11 remains in a solidstate during the heating and extruding processes while being formed withthe polymeric material or materials. In another embodiment, the low COFfilm 11 is applied to by spraying the film on the molten polymericmaterial just after the extrudate passes through the die head in thecoextrusion or triextrusion process. The film being sprayed can includeultraviolet cured films. Such an example of an ultraviolet film wouldinclude, for example, polyether acrylate with 50% nano-scale silicacurrently being sold by BASF Coatings AG under the tradename LAROMER® PO9026 V. Other types of suitable spray films can be films capable ofbeing chemically or thermally cured. In yet another embodiment, thepolymeric materials have differing compositions and durometer values asdiscussed earlier.

It will be understood that various modifications can be made withoutdeparting from the spirit and scope of the invention.

1. An annular gasket for providing a fluid-tight seal between a pair of tubular members comprising: a) a first section shaped to fit within a recess of one of a pair of tubular members; b) a second section extending from said first section and being configured to make a sealing contact with other of said pair of tubular members, said second section further comprising: i) a central tip portion at a first end of said second section; ii) a first leg portion located at a second end of said second section on a first side of said central tip portion and a second leg portion located on said second end of said second section at second side of said central tip portion; iii) a first edge portion located on the first side of said central tip portion; iv) a second edge portion located on the second side of said central tip portion; and v) a permanently lubricating film extending along said first edge portion; c) wherein said permanently lubricated film is embedded within said second section.
 2. The annular gasket of claim 1, wherein said permanently lubricating film extends from said first leg portion to said central tip portion on said first side.
 3. The annular gasket of claim 1, wherein said permanently lubricated film is a polyethylene film.
 4. The annular gasket of claim 1, wherein said permanently lubricated film is a polypropylene film.
 5. The annular gasket of claim 1, wherein said first and second sections are a single extrudate having a single durometer.
 6. The annular gasket of claim 1, wherein said first and second sections are separate extrudates having differing durometers.
 7. The annular gasket of claim 6, wherein said first section has a first durometer material and said second section has a second durometer material relatively lower than said first durometer material.
 8. The annular gasket of claim 7, wherein said first durometer material is a Shore A durometer ranging between 60-80 durometer and said second durometer material is a Shore A durometer ranging between 40-50 durometer.
 9. The annular gasket of claim 1, wherein said permanently lubricating film has a thickness ranging between 0.003″ to 0.005″.
 10. A method of manufacturing a permanently lubricated film gasket for providing a fluid-tight seal between a pair of tubular members comprising the steps of: a) providing a first material comprising a permanently lubricated film having a low coefficient of friction; b) providing a second material comprising a thermoplastic; c) loading an extruder with said first and second materials; d) heating said first and second material within a heating section of the extruder; e) feeding said first and second materials from said heating section into a die head; and f) forming a single extrusion from said first and second materials the extrusion having said permanently lubricated film along a select portion of said extrusion.
 11. The method of claim 10, wherein said permanently lubricated film is preformed.
 12. The method of claim 10, providing said second material having a first and second portion, wherein said first portion having a first durometer material and a second portion having a second durometer material relatively lower than said first durometer material.
 13. The method of claim 10, wherein said permanently lubricated film is polypropylene.
 14. The method of claim 10, wherein said permanently lubricated film is polyethylene.
 15. The method of claim 12, wherein said first durometer material, second durometer material, and said permanently lubricated film are triextruded.
 16. The method of claim 10, wherein said select portion includes a contacting portion of said second material that coacts with a surface of one of a pair of tubular members to form a sealing connection between members.
 17. A permanently lubricated film gasket for sealing adjoining pipe sections comprising: a) a first polymeric section having a first durometer circumscribing a first region of a permanently lubricated film gasket; b) a second polymeric section having a second durometer circumscribing a second region of said permanently lubricated film gasket; and c) a permanently lubricated film having a low coefficient of friction embedded along a select portion of said second polymeric section; d) wherein said first polymeric section, second polymeric section and permanently lubricated film are triextruded through a die head to form a single extrusion.
 18. The permanently lubricated film gasket of claim 17, wherein said polymeric sections are a thermoplastic.
 19. The permanently lubricated film gasket of claim 17, wherein said polymeric sections are an elastomer.
 20. The permanently lubricated film gasket of claim 17, wherein said select portion of said second polymeric section is along a leading edge of said gasket that contacts one of a pair of adjoining pipe sections to form a sealing engagement.
 21. The permanently lubricated film gasket of claim 17, wherein said low coefficient of friction is a static friction value less than 0.5.
 22. The permanently lubricated film gasket of claim 17, wherein said low coefficient of friction film remains in a controlled location on said gasket.
 23. A method of manufacturing a permanently lubricated film gasket for providing a fluid-tight seal between a pair of tubular members comprising the steps of: a) providing a first material comprising a thermoplastic; c) loading an extruder with said first material; d) heating said first material in a heating section of the extruder; e) feeding said first material from said heating section into a die head assembly; f) forming a single extrusion from said first material; and g) spraying a second material having low coefficient of friction film on said extrusion after the extrusion passes through the die head assembly, whereby the heated condition of the first material allows the second material to be embedded into the first material.
 24. The method of claim 23, wherein said film being sprayed includes an ultraviolet cured film.
 25. The method of claim 23, wherein said film being sprayed includes a thermally cured film.
 26. The method of claim 23, wherein said film being sprayed includes a chemically cured film. 